"At its best, SF is the medium in which our miserable certainty that tomorrow will be different from today in ways we can't predict, can be transmuted to a sense of excitement and anticipation, occasionally evolving into awe."
- John Brunner

This is (as far as I know) the earliest use of the phrase. It doesn't quite have the full meaning that it later acquired.

But that is impossible under the Prime Directive... Our function is to serve and obey, and guard men from harm. It is no longer necessary for men to care for themselves, because we exist to insure their safety and happiness.